Saw assembly

ABSTRACT

A saw assembly for a grip-harvester comprises a saw chain running around a bar, a pivotably journalled bar holder, and a liquid supply device having at least one nozzle for supplying at least one functional marking liquid to a cut surface produced during a sawing operation. The nozzle is mounted inside the saw box of the saw assembly and is fixed at a predetermined distance from a tree, measured at the saw cut to be executed. The nozzle is so directed that a liquid jet encounters the bar at an acute angle α(e.g. α=20-40°) and is deflected in towards the cut surface via a space between the bar and the cut surface. A control device initiates the supply of a liquid jet when the bar has been inserted a predetermined distance into the tree.

The present invention relates to a saw assembly for a grip-harvester,comprising a stand; a bar; a saw chain running around the bar and achain sprocket; a bar holder pivotably journalled on the stand; a sawmotor driving the chain sprocket; and a feeding-out and feeding-indevice for feeding the bar out and in to perform a sawing operation,said feeding-out and feeding-in device comprising a hydraulic cylindermounted on the stand and having a piston rod, and connection means totransmit the movements of the piston rod to the pivotable bar holder; asaw box in which the bar is mounted for feeding out of said box; and aliquid supply device for supplying at least one functional markingliquid to a cut surface produced during a sawing operation, which liquidsupply device comprises at least one nozzle mounted with a holder and sodirected that a liquid jet encounters an opposing side surface of thebar at an acute angle a and is deflected in towards the cut surface viaa space between the bar and the cut surface.

Grip-harvesters are used to a great extent for mechanised felling oftrees, and are equipped with hydraulically operated chain saws,generally designated saw assemblies. To achieve satisfactory operatingresults when using such saw assemblies it is particularly important thatfunctions for chain tightening and lubrication of the saw chain are welldeveloped and that certain other additional functions, such as treemarking and bar control, are also included in or in the vicinity of thesaw assembly.

A grip-harvester is an implement with which a tree can be felled, thelimbs removed and the felled tree cut into smaller pieces, the lengthsof which are dependent on the purpose to which the sawn log shall beput. The grip-harvester comprises several main components, such as arotator, a link system, a gripping unit with knives for cutting offlimbs, a trunk-feeding device, a stand, a saw box and a saw assembly.The grip-harvester is preferably freely suspended via its rotator andlink system from the tip of a forest crane which is in turn mounted on avehicle designed for being driven in forest land and other roughterrain. The vehicle with crane and grip-harvester is used both forfelling trees and at the same time removing the limbs and cutting thetree into shorter pieces. A method of operating known grip-harvesterswith known equipment can be described as follows. The operator placesthe grip-harvester against the standing tree and manipulates thegripping claws to encompass the tree. The operator then activates thesaw assembly so that the bar with saw chain swings out and cuts the treeat its lowermost part. During this phase and when the tree falls to theground a urea liquid or the equivalent shall be applied to the uppersurface of the remaining stump as efficiently as possible, without thecut surface of the cut tree being touched by the liquid.

When the tree has been felled, the operator applies the grip-harvesteron the root end of the felled tree and initiates the feed function,whereupon the tree is fed towards the de-limbing knives so that thelimbs around the trunk are cut off and removed from the trunk. While thetree is being fed along the operator also initiates feeding out the barso that, when a suitable length of the trunk has been fed along, the barwill swing out and cut off the length of de-limbed trunk that has beenfed along. The operator determines what is a suitable length dependingon the desired use to which the log shall be put, e.g. if it is to beused as timber (sawn timber), pulp wood or for some other purpose. Toenable the operator of a following machine, called a forwarder, tocorrectly sort the wood into timber, pulp and other types of cut piecesof wood when loading it, the operator of the grip-harvester must markthe surface of the logs with a colour stripe as they are cut from theoriginal tree, different colours being used for the various types oflogs cut, one colour for timber, another for pulp, etc.

The colour-marking liquid is applied to the cut surface of the cut logvia a tank system on the grip-harvester or its carrier. One of the mostusual methods of supplying the liquid is to spray it towards the cutsurface of the cut log through a nozzle on the grip-harvester's stand.It is extremely important that the nozzle is aimed at the log in such away that the liquid is sprayed on the middle of the cut surface and thatthe jet can be concentrated to produce a colour stripe across thesurface. However, this entails considerable difficulty and the method istherefore not considered to be sufficiently efficient. Another knownmethod of supplying the liquid is to spray it out through speciallyarranged channels in the bar, separate channels being arranged for eachcolour required. This method is more efficient since the liquid can besprayed onto the surface of the cut log in the right place and alsoautomatically forms a colour stripe since the supply of colour can startwhen the bar is applied against the tree to be felled and can bediscontinued when the bar has sawn off the log. However, the methodentails a great increase in cost for the bar in comparison with astandard bar, as a result of the arrangement of the channels inside thebar. This method is therefore not appreciated by the users.

In all the methods of supplying liquid described above, start and stopsignals for the supply of liquid are obtained with the aid of electronicsignals from the electronic sensor system.

In mechanised felling and processing of trees in which grip-harvestersof the type described above are preferably used, it is necessary to beable to spray out various types of functional liquids on to the cutsurface of the de-limbed and cut tree trunk at the time of sawing, in anautomatic but reliable manner. When the tree has been felled it must begraded and processed. This marking, i.e. dividing into lengths, isperformed with the aid of a marking computer in the harvester. Each logshall be marked by marking liquid being sprayed onto the cut surface ofeach individual log. Separate colours are used for the different gradesor assortments to be separated. The equipment consists of a tank for thevarious coloured liquids, a pump and a spreader. The spreader on aharvester consists either of a special bar with pre-drilled channels foreach colour and corresponding holes, or of a nozzle. In both cases thecomposition is sprayed over the end of the tree during the separationphase. The drawback of the special bar is that it is more expensive thanstandard bars, while the use of nozzles means that it may be difficultto obtain efficient marking since it may be difficult to set the correctspraying angle.

There is therefore a great need for some form of arrangement thatenables efficient colour marking of logs, while still using standardbars.

The object of the present invention is to provide a device in a sawassembly of the type described in the introduction, which enablesefficient supply of marking liquids for logs, using standard bars andeliminating current drawbacks with the use of nozzles.

The saw assembly according to the invention is characterized in that thenozzle with its holder is mounted inside the saw box, so that it is heldat a fixed predetermined distance from the tree, measured at the startof the saw cut to be executed, when gripping claws are arranged toencompass the tree and press this against a free edge of a top plate ofthe saw box, and in that the saw assembly comprises a control meansarranged to initiate supply of a liquid jet when the bar has beeninserted a predetermined distance into the tree.

The invention will be described in more detail with reference to thedrawings.

FIG. 1 shows schematically from above parts of a saw bar, partially insection.

FIG. 2 shows the saw assembly according to FIG. 1 more in section.

FIG. 3 shows the saw assembly according to FIG. 1 and illustrates itsfeeding-out and feeding-in device for the saw bar, and also a built-inlubricating oil pump.

FIG. 4 is a view of the saw assembly according to FIG. 1 seen from oneend, partially in section.

FIG. 5 is a side view of a toothed wheel and bearing means in the sawassembly according to FIG. 1, partially in section.

FIG. 6 shows a side view of a saw motor included in the saw assemblyaccording to FIG. 1.

FIG. 7 is a top view of the saw assembly and a liquid supply device withnozzles directed towards the tree.

FIG. 8 shows the saw assembly according to FIG. 7 from the open side ofa saw box in the saw assembly.

FIG. 9 is an end view of the saw assembly, partially in section,according to FIG. 8.

FIG. 10 shows schematically a nozzle in the saw assembly according toFIG. 7 and the deflection of the jet from the saw bar towards a cutsurface during commencement of a sawing operation.

FIGS. 1-4 show schematically parts of a saw assembly comprising a sawbox 13 intended for inclusion in a grip-harvester with cooperatinggripping claws 70 (see FIG. 7). The saw assembly comprises a stand 1, abar holder 2 and a bar 3 mounted on the bar holder 2 with the aid ofsuitable bar attachments and assembly devices so that a displaceableunit is formed including said bar 3. A saw chain 4 runs around the bar 3and a chain sprocket 5 (see FIG. 4), which is driven by a saw motor 6(see FIG. 6) via a drive shaft 7 (see FIG. 4) which also carries a chainguard 8. The saw motor 6 is rigidly secured inside the stand 1. The barholder 2 is pivotably journalled in relation to the stand 1 by bearingmeans 9 (see FIG. 4), to be turned in controlled manner about an axis 10coinciding with the central axis of the drive shaft 7 of the saw motor6.

Said unit is thus mounted on the bar holder 2 so that the bar 3 can bedisplaced in relation to this in a direction corresponding to thelongitudinal centre line 11 of the bar 3 and which is perpendicular tosaid axis of pivot 10. A first hydraulic piston cylinder (not shown) isarranged in one of said bar attachments to be activated by a hydrauliccircuit system of the saw assembly via a directional valve and aconnection comprising an outer pipe 12 (see FIG. 3) for displacement ofthe unit in relation to the bar holder 2 so that, during operation ofthe saw assembly, the bar 3 in the unit automatically keeps the sawchain 4 taut. A second hydraulic piston cylinder (not shown) is arrangedin one of the bar attachments to act in parallel with the axis of pivot10 in order to press against the bar holder 2 in a controlled manner toflexibly secure the movable unit to the bar holder 2. The other pistoncylinder is also affected by the pressure in said hydraulic circuitsystem via said outer pipe 12.

The saw assembly comprises a device 14 for controlled feeding of the bar3 out and in by turning the bar holder 2 about the axis of pivot 10. Thestand comprises an oblong side part 15, situated tangentially inrelation to the central stand part 16, in which the saw motor 6 issituated. The feeding-out and feeding-in device 14 comprises a hydrauliccylinder 17 which is coaxially rigidly mounted on one end of the oblongstand side part 15. The piston cylinder 18 of the hydraulic cylinder issituated behind the bar 3, seen in its direction of movement, andparallel to the bar 3 when this is in its initial position prior to asawing operation. The piston rod 19 of the hydraulic cylinder issituated in the stand side part 15 and is shaped as a rack, its sidefacing the axis of pivot 10 being provided with a section having aplurality of teeth 20—twelve teeth in the embodiment shown. Hydraulicfluid is supplied to and removed from the two pressure chambers 21, 22(see FIG. 3) of the piston cylinder 18 via pipes 23, 24 connected to thehydraulic circuit system of the saw assembly via a directional valve(not shown), which pressure chambers 21, 22 are defined by a piston 25carried by the rack 19. The feeding-out and feeding-in device 14 alsocomprises a toothed wheel 26 with a rim 27, with which the rack 19 ofthe hydraulic cylinder is in engagement. The toothed wheel 26 has acylindrical body 28 (see FIG. 4) and is rigidly joined to the bar holder2 to form a unit therewith which can be turned about said axis of pivot10. The rigid connection is achieved by means of axial bolts 29 (seeFIG. 4) which are screwed into the lower part of the toothed wheel body28 and which extend through borings in the peripheral part of the barholder 2. Said bearing means 9, which enables turning of the bar holder2, is situated within the area, i.e. within the axial extension of thetoothed wheel 26. The bearing means 9 consists of a ball bearing with anouter bearing ring 30 formed by the radially inner part of the toothedwheel 26, and an inner bearing ring 31 with which the saw motor 6 isjoined to form a rigid unit, i.e. so that the inner bearing ring 31cannot be turned about the axis of pivot 10. Between them the bearingrings 30, 31 carry balls 32 in two tracks, the ball races being out ofround so that the ball bearing functions as a four-point bearing. Theinner surface 33 of the inner bearing ring 31 is cylindrical and formsan assembly support for the corresponding externally cylindrical surface64 of a longitudinally extending assembly shaft 65 of the saw motor 6(see FIG. 6), the saw motor having an inner radial flange 66, the lowerside 67 of which rests on the radially upper surface 35 of the innerbearing ring 31, and the peripheral axial surface 68 of which cooperateswith an inner opposite axial surface 36 of the upper part 37 of thetoothed wheel body 28.

The saw assembly also comprises a lubricating oil pump 38 (see FIG. 3),arranged to provide the saw chain 4 with lubricating oil when the bar 3is fed out. In the embodiment shown the lubricating oil pump is builtinto the hydraulic cylinder 17 itself in order to form an integratedunit therewith and be served thereby. The lubricating oil pump 38comprises a central, longitudinally extending pump chamber 39 (see FIG.3) inside the rack 19 in the part facing the piston cylinder 18, andalso a central pipe 40 extending through the piston cylinder 18 and intosaid pump chamber 39 so that one end is always situated in the pumpchamber 39. The pump chamber 39 is closed off from the pressure chamber21 of the hydraulic cylinder 17 by means of suitable sealing elements 41comprising a sealing ring 42. The hydraulic cylinder 17 is closed at theend facing away from the piston rod 19 by means of a valve housing 43 inwhich said central pipe 40 extends for rigid assembly therein. The pumpchamber 39 is supplied with lubricating oil from a lubricating oil tank44 (see FIG. 3) via an outer pipe 45, a first channel 46 in the valvehousing 43 and the central pipe 40. Lubricating oil is pumped out fromthe pump chamber 39 via the central pipe 40, a second channel 47 in thevalve housing 43 and an outer pipe 48 connected to an inlet 49 in thecover 50 of the saw motor. The first and second channels 46, 47 in thevalve housing 43 are provided with non-return valves 51, 52,respectively. It will be understood that lubricant is pumped out of thepump chamber 39 when the rack 19 is moved towards the valve housing 43in order to commence a sawing operation, the volume of the pump chamber39 decreasing as a result of a larger part of the central pipe 40 beinglocated within the pump chamber 39. When the saw bar 3 is returned bythe rack 19 being moved in the opposite direction, the volume in thepump chamber 39 increases to a corresponding degree since a smaller partof the central pipe 40 will be located within the pump chamber 39. Dueto the partial pressure now arising in the pump chamber 39 the lubricantwill be sucked into the pump chamber 39 from the lubricating oil tank 44via pipe 45, channel 46 with its opened non-return valve 51 and thecentral pipe 40.

From the inlet 49 the lubricant is conveyed to the saw chain 4 viaconnections in the saw motor 6, toothed wheel 26, holder 2 and a conduit53 having its orifice close to the saw chain 4. Said connectionscomprise a circular channel formed by opposing grooves 54, 55 in theflange of the saw motor 6 and the toothed wheel 26, a channel (notshown) in the saw motor 6, which connects said inlet 49 with saidcircular channel, and radial and axial channels 56, 57 which connect thecircular channel 54 with said conduit 53 with its orifice close to thesaw chain 4.

Between them the flange of the saw motor 6 and the toothed wheel 26define a second similar circular channel in order to provide saidhydraulic piston cylinders with pressure oil via similar axial andhorizontal channels in the saw motor 6, toothed wheel 26 and holder 2from an inlet 49 in the motor cover 50. The circular channels are sealedby means of sealing rings 59 inserted in peripheral grooves.

The saw assembly also comprises a special device for sensing andrecording the angular position and also, in the embodiment shown, thedirection of movement of the saw bar 3 in relation to its home position.This device comprises a small toothed wheel 60 (see FIG. 2) which is intoothed engagement with the toothed wheel 26 of the feeding-out andfeeding-in device 14 and two sensors 61, 62 one of which, in thestarting position of the saw bar 3, is situated immediately opposite agap between two teeth, whereas the other is situated immediatelyopposite a tooth. The small toothed wheel 60 is considerably smallerthan the toothed wheel 26 of the feeding-out and feeding-in device 14 sothat a large gear ratio is obtained which, in the embodiment shown, is3.25:1. A slight rotation of the saw bar 3 thus gives a large movementon the small toothed wheel 60, which movement is sensed by the sensors61, 62. These sensors create pulse trains which are recorded andprocessed by a computer. The arrangement with two toothed wheels 26, 60with large gear ratio and sensors 61, 62 enables extremely small angularmovements of the holder 2 to be recorded, i.e. angular movements of 2°.This should be compared with known arrangements where only 7° can besensed and recorded. A sensor 63 is also provided which senses the homeposition of the rack 19 in order to indicate the home position of thesaw bar 3. One of the two sensors 61, 62, may be omitted if informationconcerning the direction of movement of the saw bar is unnecessary. Incertain cases it is sufficient if said gear ratio is 1.5:1 or more.

The saw box 13 has a top plate 71 and a bottom plate 72 which areparallel with the saw bar 3 and connected to each other by means of arear plate 73. The saw box 13 is open at its side facing away from therear plate 73 in order to permit the saw bar 3 to be fed out. The sawbox 13 is mounted on the saw assembly with the aid of the top plate 71.The bottom plate 72 is spaced from the saw bar 3 so that a gap is formedbetween them. The free edge 74 of the top plate has an inwardly running,arc-shaped extension or concave shape, the bottom area 75 of the inwardcurve lying approximately opposite the middle of the length of the sawbar 3. As can be seen more clearly in FIG. 7, the tree is receivedwithin this bottom area 75 of the inward curve.

The saw assembly is equipped with a device 76 for supply of a functionalmarking liquid to one of the cut surfaces 77 obtained at each sawingoperation. The liquid supply device 76 comprises at least one nozzle 78,arranged in a holder 79 which is screwed firmly to the inside of thebottom plate 72 of the saw box. Three nozzles 78 are used in theembodiment shown, and are arranged in the common holder 79. The holder79 is fitted in such a way that the nozzles 78 are situated at a fixedpredetermined distance from the tree 80, measured at the starting pointor commencement of the saw cut 81 to be executed, when the grippingclaws 70 encompass the tree 80 and press this against the top plate 71of the saw box 13. The saw bar 3 is thus movable in relation to thenozzle 78 and saw box 13, the nozzles 78 being stationary in relation tothe saw box 13. Said predetermined distance is about 160-180 mm,preferably about 170 mm. The nozzles 78 are directed towards an imaginedperipheral curve of the tree 80 within which the bar commences sawing atsaid saw cut 81. The invention makes use of the space 82 formed betweenthe saw bar 3 and each cut surface 77 by the saw chain 4 producing agroove 81 which is wider than the thickness of the saw bar. When the sawbar 3 has sawn to a depth substantially corresponding to the width ofthe saw bar 3, the liquid supply device 76 receives a signal to feed outthe relevant liquids which, in the form of jets 83 from the nozzles 78,are directed towards the saw bar at an acute angle α so that each liquidjet 83 is deflected into said space 82 to encounter the cut surface 77close to its periphery or a short distance in on the cut surface 77,depending on the angle of incidence α of the liquid jet 83 to the sawbar. Experiments have shown that a suitable angle α is 29°. The liquidjet 83 produces a marking on the cut surface 77 that is situated 0-50mm, preferably approximately 40 mm from the periphery of the cut surface77.

Each nozzle 78 is connected to an outer container 84 for differentfunction liquids via a connection comprising a pipe 85 provided with apump 86 and extending to the saw box 13.

The functional liquids currently applicable, i.e. that satisfy modernforestry demands, contain active components to produce colour coding orcolourless marking of the log to indicate its type and/or quality, forinstance. A colour marking can be read visually and/or optically with acolour reader, while a colourless marking is read optically with anautomatic reader or bar code reader. The operator selects the desiredcolour or colours from a computer-aided program selection system, thesecolours identifying the type of tree for instance, e.g. spruce or pine,and the kind of log, e.g. timber. The same applies to the choice ofdesired colourless liquid. Start and stop signals for the supply ofliquid are controlled with the aid of electronic signals from a controldevice with an electronic sensor system comprising said sensors 61 or 62which sense the angle of the bar holder 2 in relation to the stand 1,and a sensor on the gripping arms 70, for instance, which senses thediameter of the tree. Thanks to said tooth arrangement with the rack 19and the two toothed wheels 26, 60 with large gear ratio, the sensorsystem can sense extremely small angular movements of the bar 3, i.e. assmall as 2°, and the supply of liquid can thus be initiated at the rightmoment, i.e. at the correct position of the bar in the first part of thesaw cut, so that the liquid encounters the bar 3 in the correct positionin relation to the tree 80 and is deflected in towards the cut surface77. In other words, the liquid is aimed with extremely great precisiontowards the cut surface 77.

What is claimed is:
 1. A saw assembly for a grip-harvester, comprising:a stand; a bar; a chain sprocket; a saw chain running around said barand said chain sprocket; a bar holder pivotably journalled on saidstand; a saw motor driving said chain sprocket; a hydraulic cylindermounted on said stand and having a piston rod and a connection to saidbar holder so as to move said bar in and out to perform a sawingoperation; a liquid supply device for supplying at lest one functionalmarking liquid to a cut surface produced during a sawing operation, saidliquid supply device comprising at least one nozzle mounted with aholder and so directed that a liquid jet from said nozzle encounters anopposing side surface of said bar at an acute angle α and is deflectedin towards said cut surface in a space between said bar and said cutsurface; gripping claws for encompassing a tree; said nozzle and nozzleholder mounted inside said saw box, so that said nozzle is held at afixed predetermined distance from a tree measured at said start of saidsaw cut to be executed when said gripping claws are positioned toencompass a tree and press said tree against said free edge of said topplate of said saw box; and control means for initiating a supply of aliquid jet from said nozzle when said bar has been inserted apredetermined distance into said tree.
 2. A saw assembly as claimed inclaim 1 wherein said angle α is between 20° and 40°.
 3. A saw assemblyas claimed in claim 1 wherein said angle α is between 25° and 35°.
 4. Asaw assembly as claimed in claim 1 wherein said angle α is between 29°and 31°.
 5. A saw assembly as claimed in claim 1 wherein the liquid jetproduces a marking in the cut surface which is located 0-50 mm from theperiphery of the cut surface.
 6. A saw assembly as claimed in claim 1,wherein said connection comprises a first toothed wheel pivotablyjournalled in said stand, and coaxially, rigidly joined to said barholder, at least a sector of a first toothed wheel rim mounted levelwith and facing said piston rod and level with and facing said pistonrod; and wherein said piston rod includes a rack with teeth facing saidfirst toothed wheel and in engagement with said teeth on said at least asector of said rim; and further comprising a device for sensing andrecording the angular position of said saw bar in relation to an initialposition, said sensing and recording device comprising a second toothedwheel which is smaller than and is in toothed engagement with said firsttoothed wheel so that a gear ratio of >1 is obtained, said sensing andrecording device including at least one sensor which, in an initialposition of said saw bar, is positioned immediately opposite a gapbetween two teeth or immediately opposite a tooth in said second toothedwheel.
 7. A saw assembly as claimed in claim 6 wherein said sensingdevice also senses and records the direction of movement of said sawbar, said sensing and recording device comprising two sensors one ofwhich in an initial position of said saw bar is positioned immediatelyopposite a gap between two teeth, and the other immediately opposite atooth on said second toothed wheel.
 8. A saw assembly as claimed inclaim 7 wherein the gear ratio between said first and second toothedwheels is greater than 1.5:1.
 9. A saw assembly as claimed in claim 6wherein the gear ratio between said first and second toothed wheels isgreater than 1.5:1.
 10. A saw assembly as claimed in claim 6 wherein thegear ratio between said first and second toothed wheels is greater than3:1.
 11. A saw assembly as claimed in claim 7 wherein the gear ratiobetween said first and second toothed wheels is greater than 3:1.
 12. Asaw assembly as claimed in claim 6 further comprising a bearingpositioned within the axial extension of said first toothed wheel topermit turning of said bar holder.
 13. A saw assembly as claimed inclaim 1 wherein said saw box has a bottom plate, and wherein said nozzleholder is mounted on the inside of said bottom plate of said saw box.14. A saw assembly as claimed in claim 1 wherein said at least onenozzle comprises three nozzles for supplying different marking liquidsto produce differently colored or otherwise visually or opticallyreadable different markings at separate points on the cut surface.
 15. Asaw assembly as claimed in claim 1 wherein said predetermined distancebetween said at least one nozzle and the saw cut is about 160-180 mm.16. A saw assembly as claimed in claim 1 wherein the liquid jet producesa marking in the cut surface which is located 40 mm from the peripheryof the cut surface.
 17. A saw assembly as claimed in claim 1 whereinsaid predetermined distance between said at least one nozzle and the sawcut is about 170 mm.
 18. A saw assembly as claimed in claim 2, whereinsaid connection comprises a first toothed wheel pivotably journalled insaid stand, and coaxially, rigidly joined to said bar holder, at least asector of a first toothed wheel rim mounted level with and facing saidpiston rod and level with and facing said piston rod; and wherein saidpiston rod includes a rack with teeth facing said first toothed wheeland in engagement with said teeth on said at least a sector of said rim;and further comprising a device for sensing and recording the angularposition of said saw bar in relation to an initial position, saidsensing and recording device comprising a second toothed wheel which issmaller than and is in toothed engagement with said first toothed wheelso that a gear ratio of >1 is obtained, said sensing and recordingdevice including at least one sensor which, in an initial position ofsaid saw bar, is positioned immediately opposite a gap between two teethor immediately opposite a tooth in said second toothed wheel.
 19. A sawassembly as claimed in claim 18 wherein the liquid jet produces amarking in the cut surface which is located 0-50 mm from the peripheryof the cut surface.
 20. A saw assembly as claimed in claim 19 whereinsaid predetermined distance between said at least one nozzle and the sawcut is about 160-180 mm.